<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html>
<head>
    <title>学生主页</title>
</head>
<body>
<%
    String userId = (String) request.getSession().getAttribute("user_id");
    if (userId != null) {
%>
<h1>欢迎, <%= userId %>!</h1>
<%
} else {
%>
<h1>未登录或会话已过期</h1>
<p>请<a href="Landing_page.jsp">重新登录</a>。</p>
<%
    }
%>
</body>
</html>
